Showing papers on "Dynamic pressure published in 2023"
3 citations
TL;DR: In this paper , the authors explore if an approximate unsteady pressure distribution can be created experimentally in a simple aerodynamic tunnel by composing a sequence of blade surface steady pressures acquired for gradually varying blade incidence angle offsets.
Abstract:
A lack of reliable experimental data on transonic blade flutter in real turbomachines hampers further improvement of computational design predictions for off-design operation regimes of newly built machines. Acquiring unsteady pressure distributions on blades in real turbomachines is practically impossible. The goal of this work is to explore if an approximate unsteady pressure distributions can be created experimentally in a simple aerodynamic tunnel by composing a sequence of blade surface steady pressures acquired for gradually varying blade incidence angle offsets. An essential condition for such an approximation is that the dynamic pressure component induced by the blade motion is substantially smaller than the flow pattern changes caused by the varying interblade channel geometry. A dedicated test facility, called the Blade Flutter Module (BFM), has been built and used for this purpose. The BFM is a linear cascade consisting of five transonic airfoils that can be operated either in a static or a dynamic regime. For the dynamic operation, any of the blades can be oscillated at frequencies of up to 400 Hz with the maximum angular amplitude of three degrees. The obtained results confirm that within the range of the test conditions, the proposed compounded quasi-dynamic approach exhibits similar characteristics to dynamically acquired unsteady blade pressures. This is true for a test range of a maximum inlet Mach number of 1.09, maximum blade oscillating frequency of 100 Hz, and measurement of unsteady pressure distributions on a blade suction surface. The corresponding blade reduced frequency is 0.21.
1 citations
TL;DR: In this article , the authors used computed fluid dynamics (CFD) simulation and real data from the pressure measurement system for determination of the dynamical model of the Pitot tube with the transducer.
Abstract: This paper presents an attempt to determine the dynamic properties of a measuring system based on total pressure measurement with the use of a Pitot tube and a semiconductor pressure transducer. The presented research uses computed fluid dynamics (CFD) simulation and real data from the pressure measurement system for determination of the dynamical model of the Pitot tube with the transducer. An identification algorithm is applied to the data from the simulation, and the model in the form of a transfer function is an identification result. The oscillatory behavior is detected, and this result is confirmed by frequency analysis of the recorded pressure measurements. One of the resonant frequencies is the same in both experiments, but the second is slightly different. The identified dynamical models permit the possibility to predict deviations caused by dynamics and to select the appropriate tube for a particular experiment.
1 citations
TL;DR: In this paper , the authors present a theoretical study on the dynamic performance of an aerostatic pad with an internal pressure control and analyze the trend of the dynamic stiffness and damping over the frequency domain.
Abstract: Abstract. This paper presents a theoretical study on the dynamic performance of an aerostatic pad with an internal pressure control. The trend of the dynamic stiffness and damping over the frequency domain is analysed.
TL;DR: In this article , the authors analyzed the effect of dynamic pressure during the climb phase on the corona inception voltage and showed that the dynamic pressure conditions do not have a significant effect on the CORona inception value under typical conditions found in aircraft systems during the climbing phase.
Abstract: The combination of the low-pressure environment found in aircraft systems and the gradual electrification of aircraft increases the risk of electrical discharges occurrence. This is an undesirable situation that compromises aircraft safety and complicates maintenance operations. Experimental data are needed to understand this problem. However, most of the published studies are based on static pressure conditions, but aircraft systems are exposed to dynamic pressure conditions, especially during the climb and descent phases of flight. This paper analyzes the effect of dynamic pressure during the climb phase on the corona inception voltage because this phase experiences the worst pressure drop rate. The experimental evidence presented in this paper shows that within the analyzed pressure drop rate range, the dynamic pressure conditions do not have a significant effect on the corona inception value under typical conditions found in aircraft systems during the climb phase.
TL;DR: In this article , a convenient and adjustable PVC-U (unplasticized polyvinyl chloride) shock tube is developed to study the dynamic calibration method of the shock tube of the blast pressure pencil probes, such as free-field pressure sensors and dynamic pressure sensors.
Abstract: Dynamic calibration is one of the important ways to obtain the dynamic performance parameters of pressure sensors, and shock tube calibration is a common method for dynamic calibration of pressure sensors. To study the dynamic calibration method of the shock tube of the blast pressure pencil probes, such as free-field pressure sensors and dynamic pressure sensors, a convenient and adjustable PVC-U (unplasticized polyvinyl chloride) shock tube is developed. Taking the dynamic pressure sensor as the research object, the feasibility of dynamic calibration of shock tube based on CFD (Computational Fluid Dynamics) techniques is discussed. Finally, the dynamic calibration experiment based on shock tube is carried out, and the time-domain and frequency-domain signals are analyzed. The results are in good agreement with the theoretical analysis. The results show that the shock tube can effectively excite the natural frequency of the dynamic pressure sensor, and the developed shock tube can indeed achieve the dynamic calibration and dynamic experiments of pencil probes.
TL;DR: In this article , the authors analyzed the long-term global navigation satellite system (GNSS) total electron content (TEC) data from 2000 to 2018 and performed a superposed epoch analysis of the GNSS rate of the ROTI, solar wind, interplanetary magnetic field (IMF), and geomagnetic index.
Abstract: To elucidate the effect of solar wind dynamic pressure on the activities of ionospheric plasma irregularities in both high-latitude and equatorial regions, we analyzed the long-term global navigation satellite system (GNSS) total electron content (TEC) data from 2000 to 2018 and performed a superposed epoch analysis of the GNSS rate of the TEC index (ROTI), solar wind, interplanetary magnetic field (IMF), and geomagnetic index. We found that during the main phase of geomagnetic storms, the activities of ionospheric plasma irregularities were considerably enhanced in both high-latitude and equatorial regions under high-pressure conditions, and the equatorward edge of the auroral oval moved to lower latitudes. The poleward edge of the enhanced low-latitude ROTI region (occurrence region of the plasma bubbles) in the evening sector extended to higher latitudes under high-pressure conditions. During the recovery phase of geomagnetic storms, the plasma bubble occurrence in the dusk sector was suppressed under high-pressure conditions. Our results suggest that the high-latitude convection electric field and the penetration and disturbance dynamo electric fields at low latitudes become stronger during geomagnetic storms when the solar wind dynamic pressure is enhanced. This is because the conversion from solar wind energy to electromagnetic energy in the magnetosphere is enhanced by the formation of a high plasma pressure area in the high-latitude cusp and mantle region. Therefore, not only the southward IMF but also solar wind dynamic pressure are important factors for varying global ionospheric responses during geomagnetic storms.
15 May 2023
TL;DR: In this paper , the authors report a solar wind dynamic pressure enhancement followed by an interplanetary magnetic field clock angle change on February 13, 2014 and use the University of Michigan Space Weather Framework (SWMF) to conduct numerical simulations to explain the differences in the interhemispheric responses to the changes in solar wind dynamics and IMF clock angle together and separately.
Abstract: With the increased availability of ground magnetic field measurements from the Northern and Southern hemispheres at higher latitudes, further insight could be gained into how the physical processes coupling magnetosphere and ionosphere vary with solar wind forcing. In this study, we report a solar wind dynamic pressure enhancement followed by an interplanetary magnetic field clock angle change on February 13, 2014. We use measurements from East Antarctica and West Greenland regions to investigate when and where the magnetic field signatures differ. Finally, we use the University of Michigan Space Weather Framework (SWMF) to conduct numerical simulations to explain the differences in the interhemispheric responses to the changes in solar wind dynamic pressure enhancement and IMF clock angle together and separately.  This work is supported by NASA LWS Program and makes use of the NASA High-End Computing Capability.
TL;DR: In this paper , the dynamic pressure under wave crests is experimentally studied in three different scenarios, and the influence of nonlinearity as well as the dispersive effect is revealed by comparing with the corresponding linear theoretical predictions.
TL;DR: In this paper , a dynamic pressure control method based on the model reference sliding mode theory is designed to satisfy the strict requirements of dynamic pressure for air-breathing hypersonic vehicle during the initiation, and the simulation results show that the designed control system can accurately track the dynamic pressure command with great robustness.
Abstract: Abstract To satisfy the strict requirements of dynamic pressure for air-breathing hypersonic vehicle during the initiation, a dynamic pressure control method based on the model reference sliding mode theory is designed. Firstly, the motion equation of the air-breathing hypersonic vehicle is built, and the dynamic pressure linearization model is established by the small perturbation method. Secondly, the control system, designed by the model reference sliding mode control theory, can quickly track the reference model. Finally, the six degrees of freedom simulation model is built and used for digital simulation. The simulation results show that the designed control system can accurately track the dynamic pressure command with great robustness.
TL;DR: In this paper , an in-flight angle of attack (α) measurement system based on pressure measurements at the surface of the nosecone for low apogee rockets was proposed, where an electronic micro differential pressure transducer was selected to measure the pressure difference between selected points in the rocket's nosecone.
Abstract: The angle of attack (α) affects the drag, flight path, and flight stability during rocket ascent. This work proposes an in-flight α measurement system based on pressure measurements at the surface of the nosecone for low apogee rockets. An electronic micro differential pressure transducer was selected to measure the pressure difference between selected points in the rocket’s nosecone. Wind tunnel tests were performed to correlate the α with the sensor output at low Mach numbers (Ma ≃ 0.08). The experimental results were further used as a reference for the construction of CFD models of the external flow in the rocket’s nosecone with the aim of predicting the measurements in an extended Mach number range (up to Ma ≃ 0.7). The numerical results allowed for an extended model correlating α with the differential pressure transducer output (Ch). The estimate of model’s errors completes the analysis.
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TL;DR: In this paper , the dynamic pressure rise or fall in all kinds of pipelines due to the operation of the valve which are transmitting fluids are very much essential part to consider in the design of pipeline.
Abstract: Dynamic Pressure rise or fall in all kinds of pipelines due to the operation of the valve which are transmitting fluids are very much essential part to consider in the design of pipeline. This paper presents how to calculate these dynamic pressure waves while designing pipelines.
TL;DR: In this paper , a model-based and easy-to-implement approach to calibrate the dynamic strain-pressure sensitivity coefficient (DSSC) is proposed to compensate the dynamic pressure.
TL;DR: In this article , the authors measured the aerodynamic performance and dynamic pressure signals of a compressor cascade platform with high-speed rotating endwall and found that endwall movement amplifies circumferential leakage losses, increases kinetic energy, deviates the leakage flow path, and reduces total pressure loss in the leakage core region.
Abstract: Abstract This study measured the aerodynamic performance and dynamic pressure signals of a compressor cascade platform with high-speed rotating endwall. Instead of translational movement, the endwall features an innovative large rotating disk. Measurements were conducted on a controlled diffusion airfoil (CDA) under different conditions: tip clearances (3 mm and 2.5 mm), inlet incidences (+6° and −6°), and stationary or high-speed rotating states at 0.5 Ma inflow. The results reveal that endwall movement amplifies circumferential leakage losses, increases kinetic energy, deviates the leakage flow path, and reduces total pressure loss in the leakage core region. Dynamic pressure results reveal greater unsteadiness in the tip region under positive incidence conditions and with larger clearances. Characteristic frequency ranges (8000 Hz for system vibration and 150∼200 Hz for leakage flow development) are identified. Further experimental measurements and high-precision simulations are needed the determine the matching relationship between complex flow behaviour in the blade tip region and characteristic frequency.
TL;DR: In this paper , the authors reviewed the current progress in this field, specifically the prompt responses of chorus waves and plasmaspheric hiss to the solar wind dynamic pressure pulses, and summarized the underlying mechanisms and pose some outstanding questions.
Abstract: Whistler-mode waves play a critical role in shaping the Earth’s radiation belts, and their spatiotemporal distribution is vital for forecasting and modeling geospace weather. Previous works have extensively investigated the influences of geomagnetic activities, such as storms and substorms, on the modification of whistler-mode waves, but the direct impacts of solar wind disturbances have received relatively less attention. Recently, increasing research has highlighted the prompt impacts of solar wind dynamic pressure pulses on magnetospheric whistler-mode waves. This paper reviews the current progress in this field, specifically the prompt responses of chorus waves and plasmaspheric hiss to the solar wind dynamic pressure pulses. It will summarize the underlying mechanisms and pose some outstanding questions.
19 Jan 2023
TL;DR: In this paper , the authors present longitudinal dynamic derivatives of a flying wing configuration, SACCON, at low and mildly high angle of attacks in nonlinear regions, which can be used to generate data for fly-by-wire flight computers.
Abstract: We present longitudinal dynamic derivatives of a flying wing configuration, SACCON, at low and mildly high angle of attacks in nonlinear regions. The time – depending governing equations are solved with Reynolds-Averaged Navier-Stokes model for both static and dynamic parameters. The dynamic maneuver of the aircraft is simulated with simple harmonic oscillatory motion. Dynamic derivatives change suddenly in nonlinear regions; hence, the constant dynamic derivative assumption is not valid for these regimes. The two different dynamic derivative estimation methods used here produce similar values at relatively small angle of attacks, whereas they yield different values at large angle of attacks. In addition, the dominant frequencies of dynamic oscillation at two different angles present coinciding frequencies that could be the trace of the same vortex mechanism. The estimation of dynamic derivatives and the mentioned phenomena through CFD can assist aircraft maneuverability prediction in early design states and can be used to generate data for fly-by- wire flight computers.
TL;DR: In this article , the dynamic Reynolds equation group, with the stiffness and damping pressure written separately, is removed and numerically solved with a high-pressure boundary for a parallel flat and circular thin film.
Abstract: The squeeze film effect was discussed in several fields, but mostly under the same pressure boundary conditions. However, pressures at the inlet and outlet are different for aerostatic bearings. In this paper, the dynamic Reynolds equation group, with the stiffness and damping pressure written separately, is deducted and numerically solved with a high-pressure boundary for a parallel flat and circular thin film. The circular thin film considers the two results of the supply pressure boundary inside and outside. All dynamic pressure distribution and stiffness curves are given in a dimensionless form, and a comparative analysis of squeeze film characteristics with and without external pressure is conducted. From the calculation results, it can be concluded that the squeeze effect shows damping for zero-frequency and stiffness for infinite-frequency for compressible lubricants. The dynamic pressure in the static high pressure region is also high at high frequencies affected by gas compressibility. Based on these analytical results, the transfer functions of the thin film are given to further analyze the dynamic performance of aerostatic bearings, and the shape of the response curve approximates an exponential decay form, even when the amplitude increases to 10% of the gas film thickness.
01 Jan 2023
24 Apr 2023
TL;DR: In this article , the dynamic pressure effect of the clearance oil film of a stepped hydrostatic thrust bearing is studied by taking the double rectangular cavity oil cushion as an example. And the authors show that the theoretical value of the average dynamic pressure and the rotational speed show a linear growth relationship with a slope of 275.2.
Abstract: Abstract The dynamic pressure effect of the clearance oil film of stepped hydrostatic thrust bearing is studied by taking the double rectangular cavity oil cushion as an example. According to the hydrodynamics theory, the average dynamic pressure of lubricating oil film in different clearance height regions is theoretically deduced and calculated, and the dynamic pressure effect of the clearance oil film in the stepped hydrostatic thrust bearing is studied through the combination of theoretical calculation, simulation, and experimental verification. It is found that the theoretical value of the average dynamic pressure of the clearance oil film and the rotational speed show a linear growth relationship with a slope of 275.2. The simulated value of the average dynamic pressure and the rotational speed follow the growth law of the Fourier 1 model. The experimental value of the average dynamic pressure is between the theoretical value and the simulated value, which is basically not affected by the load. In the speed range of 0r/min-200r/min, compared with the viscosity of lubricating oil, the speed is the main factor affecting the dynamic pressure of the oil film of the stepped hydrostatic thrust bearing. The dynamic pressure value of the clearance oil film increases in a stepped fashion along the radial direction of the double rectangular cavity oil cushion. The dynamic pressure value has an obvious upward trend at the junction of the circumferential right oil cavity and the sealing edge and then decreases to 0 after reaching the peak value.
17 Jan 2023
TL;DR: In this article , a balloon-type dielectric elastomer actuator (DEA) pre-stretched by water pressure was analyzed and an analytical solution for dynamic characteristics of this DEA based on a physical model of this experimental system was derived.
Abstract: In this paper, we analyzed dynamic characteristics of a balloon-type dielectric elastomer actuator (DEA) pre-stretched by water pressure. We derived an analytical solution for dynamic characteristics of this DEA based on a physical model of this experimental system. This experimental system consists of an elastomer attached on an acrylic pipe and a water reservoir connected to the acrylic pipe with a hose. Therefore, by changing parameters of these equipment, dynamic characteristics will be changed. We analyzed frequency response of the DEA when we changed these parameters and compared experimental values with theoretical values. Also, we analyzed dynamic responses when various electric voltages were applied to the DEA. The analytical solution can predict frequency responses and dynamic response. In addition, we conducted open loop control of displacement of the DEA. Deformations of DEA was able to be controlled according to desired displacement with the constructed model.
TL;DR: In this paper , a 3D multifluid multispecies numerical model is established to simulate the interaction between solar wind and Mars, and functions of electromagnetic forces applied on different ion species were analyzed.
Abstract: Disturbed solar wind dynamic pressure is one of the important external drivers which could cause significant impacts on Martian plasma environment. In this study, a 3D multifluid multispecies numerical model is established to simulate the interaction between solar wind and Mars. Functions of electromagnetic forces applied on different ion species were analyzed. We found that the total electromagnetic force peaks near bow shock (BS) and magnetic pileup boundary (MPB) with clear asymmetry features, acting to decelerate solar wind plasma across boundary layers, and compresses heavy ions toward the planet inside the MPB. For solar wind protons, electron pressure gradient force dominates near BS and Hall electric field force dominates near MPB, controlling the location of plasma boundary. Furthermore, the morphology of motional electric field force shows clear north-south asymmetry, leading to the formation of asymmetric structures and plasma flow in Martian space environment. The response of BS, MPB to a solar wind dynamic pressure enhancement event, as well as the effects of electromagnetic forces in this process are also investigated. After the arrival of solar wind pulse, the magnitudes of electromagnetic forces increased simultaneously to balance the enhanced solar wind dynamic pressure, while the peaks of forces moved inward with BS and MPB. The magnitudes and peaks of ion velocity in subsolar region show similar variations as well, with the greater enhancement of forces leading to the greater increase of ion velocities, indicating that the changes of forces influence boundary layers through the variation of plasma speed.
16 Apr 2023
TL;DR: In this article , the authors presented ultra-low frequency (ULF) Pc5 discrete spectrum simultaneously observed in the magnetosphere and high-to-low-latitude ionospheres near noon hours (~10-14 MLT) during the recovery phase of geomagnetic storm on November 4, 2021.
Abstract: This study presents ultra-low frequency (ULF) Pc5 discrete spectrum simultaneously observed in the magnetosphere and high- to low-latitude ionospheres near noon hours (~10-14 MLT) during the recovery phase of geomagnetic storm on November 4, 2021. During the recovery phase, magnetospheric toroidal mode oscillations (GOES-16 Bn) appeared according to solar wind dynamic pressure enhancements after GOES Bp and Be (poloidal mode) oscillations precede during high solar wind speeds. When Bn oscillates, the ionospheric line-of-sight (LOS) velocity and echo power oscillate at the same discrete frequencies of 1.7 and 2.2 mHz (9.7 and 7.5 min), observed by Super Dual Auroral Radar Network (SuperDARN) at Saskatoon (eastward LOS). The period of negative LOS velocity (away from the radar) for 7.5 min or 9.7 min corresponds to echo power increase. This signifies that both the ionospheric density and poleward convection velocity increase are driven by the periodic forcing of the convection electric field and energetic electron precipitation. The same frequency pulsations have also been observed in the geomagnetic field (H-component) and Global Positioning System (GPS) total electron content (TEC) from high- to low-latitude ionosphere. The oscillation frequency of the H-component is consistently preserved at 1.7 mHz (9.7 min) down to low latitudes. The Pc5 oscillations at high to low latitudes can be attributed to toroidal mode Alfven waves and the compressional mode propagating across magnetic field lines as well as the fast magnetosonic waveguide mode at work by the solar wind dynamic pressure enhancements at high solar wind speeds.
01 Jan 2023
TL;DR: In this paper , shake table tests on small-scale models of retaining walls were conducted to investigate the effectiveness of geofoam compressible inclusions as a seismic isolator to lessen dynamic loads against retaining wall structures.
Abstract: Earth retaining walls should be built to withstand both static and dynamic increments in earth pressure, particularly in earthquake-prone areas. Various earlier types of research suggest that geofoam inclusions are effective in reducing the dynamic earth pressure on the cantilever retaining wall. In this research, shake table tests on small-scale models of retaining walls were conducted to investigate the effectiveness of geofoam compressible inclusions as a seismic isolator to lessen dynamic loads against retaining wall structures. The results of these tests are compared to those of identical models of retaining walls with backfill only and without any inclusion. Experimental investigation shows that dynamic earth pressure and wall displacement reduced up to 35% and 40%, respectively.
TL;DR: In this article , the application of a cross-flow fan (CFF) to generate propulsion for a submersible aircraft with a flying wing configuration was investigated. And the authors provided a valuable numerical methodology for studying the fluid dynamic characteristics of the CFF operating in different media.
Abstract: This paper focuses on the application of a cross-flow fan (CFF) to generate propulsion for a submersible aircraft with a flying wing configuration. A numerical method is established to simulate the CFF operating both in the air and underwater. This paper then investigates the fluid dynamic characteristics of the CFF, including the velocity field, the pressure field, the cavitation distribution, the lift, and the thrust. It is concluded that proper lifts and thrusts can be obtained when the rotating speed and the angle of attack are reasonably designed. This work provides a valuable numerical methodology for studying the fluid dynamic characteristics of the CFF operating in different media and offers a technical basis for the selection of a motor system for submersible aircraft.